OK Cells

The OK cell line is a permanent epithelial-like cell culture derived from kidney tissue of an adult female American opossum (Didelphis virginiana). Established in vitro, this cell line is notable for its non-diploid chromosomal modal number of 23 and its adaptability to tissue culture conditions. Initially derived from mixed cell types, the culture evolved into predominantly epithelial cells after eight passages. The OK cell line has been extensively characterized in terms of morphology, chromosomal constitution, and growth dynamics, making it a robust model for cytogenetic and chromosome isolation studies.

One of the key features of the OK cell line is its utility in chromosome studies, especially for isolating the mammalian X chromosome. The opossum X chromosome is significantly smaller (approximately 30% smaller than the smallest autosomes) and does not contain large blocks of constitutive heterochromatin, facilitating separation from autosomes through techniques like flow microfluorometry and gradient centrifugation. The stable karyotype of the OK cells, with the presence of a distinctive metacentric marker chromosome, enhances their application in genomic and chromosomal studies. The paternal X chromosome’s preferential inactivation in this marsupial provides a comparative model for studying mechanisms underlying X-chromosome inactivation in mammals.

OK cells have also demonstrated resilience and adaptability in various culture conditions, including serum variations and different mitotic-arresting agents like Velban (vinblastine sulfate), which is particularly effective for achieving high mitotic indices for chromosome isolation. The cell line’s ability to synchronize and produce high yields of metaphase cells further underscores its suitability for detailed chromosomal analyses, including DNA content quantification and high-resolution imaging of chromosomal spreads.